Soft-matter aggregates that can entrap small volumes of water have since long been investigated in delivery of pharmaceuticals (e.g. small molecules, proteins, DNA) to the body. A popular example is vesicles formed from liposomes, which are microscopic hollow spheres where a thin bilayer lipid membrane encloses a volume of water. Although liposomes are potentially well-suited for compound delivery, they suffer from the inherent instability of the thin lipid bilayer membrane. Hence, recently options have been explored in which the amphiphile is not based on lipids, but rather on amphiphilic block or random copolymers or proteins.
Apart from vesicular structures, other self-assembled architectures that can form from lipids or amphiphilic molecules include micellar, sheet-like and tubular architectures. The latter architecture is especially interesting for in-vivo applications since they show characteristic clearance behaviour.